Cardiotomy reservoirs are currently used in major surgical procedures, such as open heart surgery, for receiving blood from a cardiotomy sucker and other sources, for defoaming the blood, filtering out debris, and returning it to the patient.
In U.S. Application Ser. No. 901,323 filed May 30, 1978, by Thomas W. Crockett, et al. and entitled "Improved Cardiotomy Reservoir", a reservoir for blood is disclosed, having a rigid casing and a perforated tubular member positioned within the casing and extending between the ends thereof. Blood defoaming material is positioned within the tubular member, and a filter is carried by the tubular member so that blood clots and larger bubbles cannot escape from the interior of the filter member to the exterior.
Other designs of cardiotomy reservoirs are known, for example, a cardiotomy reservoir similar to that disclosed in U.S. Pat. No. 3,993,461, its predecessor in design being as disclosed in U.S. Pat. No. 3,891,416. In both of these cardiotomy reservoirs, a hollow casing is provided in which a tubular member is positioned within the casing and extends between the ends thereof. Blood enters the bottom of the tubular member rising upwardly until it passes out of an aperture to the exterior of the tubular member.
In accordance with this invention, the above described type of cardiotomy reservoir is improved by the use of a double stage defoaming structure.
As in the previously cited patent application, the defoaming sponge within the tubular member may be surrounded by a fine weave filter netting, which confines large gas bubbles to the region containing the first defoaming sponge material. Small bubbles, however, may pass through the filter screen.
In the structure of this invention, those small bubbles which do pass through the filter screen to the area which is outside of the tubular member encounter a second defoaming sponge, where they also are broken down. Unlike the situation in the first defoaming means, the second stage can dissipate the fine bubbles without interference from the large bubbles, which can tend to create small bubbles and inhibit their dissipation.
Also, the structure of this invention may be adapted so that small bubbles which are formed or otherwise reside within the reservoir outside of the tubular member and fine weave filter netting may easily enter into contact with the second defoaming means for further bubble removal.